Reversible Photochromism for Dynamically Tuning Full-Color Circularly Polarized Luminescence Toward Multi-Level Anti-Counterfeiting Application

Photochromic circularly polarized luminescence (CPL) demonstrates broad application prospects in the field of advanced functional materials. However, the current photochromic CPL focuses predominantly on single-band CPL adjustment, and how to achieve dynamically tunable CPL in multi-band is still highly challenging. This work reports the success in utilizing reversible photochromism for realizing full-color CPL emission. Photochromic flexible films are created consisting of triple components: spiropyran (SP) working as photochromic matter, polyurethane (PU) as matrix, and chiral helical polyacetylene as chiral component. Further introducing blue fluorophore 9-anthracene carboxylic acid (ACA) in the film, blue CPL and red CPL are emitted respectively through selective absorption/transmission and circularly polarized fluorescence energy transfer (CPF-ET). Doping the photochromic film with diverse fluorophores provides full-color CPL emission. Adding Zn 2+ further intensifies fluorescence and CPL via forming merocyanine (MC)-Zn 2+ complex. Taking advantage of the diverse fluorescence and CPL emission, anti-counterfeiting, and secondary encryption application of the resulting photochromic CPL materials are demonstrated.